A single frequency network (SFN) is a powerful way to achieve large coverage areas in many digital broadcasting schemes, such as, for example, Digital Video Broadcasting for Terrestrial (DVB-T), Digital Video Broadcasting for Handheld Mobile Television (DVB-H), and Advanced Television Systems Committee (ATSC) broadcasting as SFNs allow transmitters to extend their area of coverage without using a second channel. This is important because portions of an available broadcast spectrum are one of the most expensive commodities in broadcast networks.
Signals feeding all transmitters in SFN systems must be totally synchronous (i.e., the signal must contain the very same bit stream and reach the transmitter within fixed time tolerances). In large systems, different areas are covered by SFN transmitters that have partially different content (e.g., insertion of regional content). As a result, different bit streams are required at different SFN areas. A traditional telecom approach to support such a system is to transport elementary signals to SFN nodal points, multiplex signals to create different streams for each SFN, and provide dedicated feeds to SFN transmitters. However, such an arrangement is very expensive and fragile when large areas (e.g., countries or continents) are covered with thousands of transmitters. Other approaches use satellite feeds to deliver signals by multiplexing all SFN signals together. Unfortunately, broadcasting all streams in parallel when many variants are required is also expensive since bandwidth increases linearly with the number of SFN areas. Therefore, improved broadcasting schemes are needed for multiple transmitters servicing a large SFN.